Reticulocyte Production Index (RPI)

Norm of Reticulocyte Production Index (RPI)

Index of 1.
Accelerated red blood cell production.
Alcoholism; anemia (aplastic, iron deficiency, megaloblastic, pernicious, pure red cell); aregenerative crisis; aplastic crisis of hemolytic anemia; chronic infection; myxedema; and radiation therapy.


Description of Reticulocyte Production Index (RPI)

The reticulocyte production index (RPI) is a calculated measurement of the number of circulating reticulocytes in the packed cell volume of hematocrit. The raw reticulocyte count is expressed as a percentage of erythrocytes. In anemia, a 1%–2% reticulocyte count is not really normal because it is based on a lower-than-normal amount of erythrocytes. Also, the normal life span of reticulocytes is 2 days, but in the presence of accelerated red blood cell production, reticulocytes are released prematurely and circulate for up to 4 days. The RPI normalizes the reticulocyte count by multiplying it by the hematocrit divided by 45 and by correcting for the increased life span of reticulocytes (based on the degree of anemia) to give a more accurate portrayal of the rate of reticulocyte production. This index is used to calculate the degree of increased erythropoietic activity associated with the premature release of reticulocytes (shift) from the bone marrow in anemia.


Professional Considerations of Reticulocyte Production Index (RPI)

Consent form NOT required.

  1. See Reticulocyte count—Blood; Hematocrit—Blood.
  2. Do NOT draw specimens during hemodialysis.



  1. Obtain samples for reticulocyte count and for VPRC (volume of packed red cells, hematocrit). See Reticulocyte count—Blood ; Hematocrit—Blood.
  2. Calculation: Reticulocyte maturation time in the circulating blood changes as follows:
Reticulocyte Maturation Time
35 1.5 days
30 1.75 days
25 2.0 days
20 2.25 days
15 2.5 days

The RPI is calculated as:
RPI=Reticulocyte%/Reticulocyte maturation time (days) x Client's VPRC (1)/0.45


Postprocedure Care

  1. See Reticulocyte count—Blood ; Hematocrit—Blood.


Client and Family Teaching

  1. This test measures the number of immature red blood cells in your bloodstream.
  2. Results are normally available within 24 hours.


Factors That Affect Results

  1. See Reticulocyte count—Blood ; Hematocrit—Blood.


Other Data

  1. See Reticulocyte count—Blood ; Hematocrit—Blood.